Effect of position of heat flux profile on the absorber surface of parabolic trough solar collector for direct steam generation

Abstract

The overall performance of parabolic trough solar collector (PTSC) based power plants could be improved by introducing the Direct steam generation (DSG) in the receiver of the solar collector. However, the thermal-hydraulic instability induced in the DSG process is a severe issue for the commercial application of the technology. The concentrated solar flux falling on the dry portion of the absorber before or after solar noon generates a high circumferential thermal gradient in the stratified flow region. In this work, numerical analysis of thermo-hydrodynamics of DSG has been performed to study the effect of position of solar flux profile using CFD solver ANSYS Fluent 2020R1. The TPF in the solar collectors is modeled through two-fluid modeling approach. The inlet mass flow rate and operating pressure for PTSC are considered as 0.6 kg/s, and 100 bar, respectively. The solar beam radiations are considered as 750 W/m2 and 1000 W/m2. The obtained results revealed that temperature distribution at the absorber outer surface varies in the range of 585 K to 643 K. The maximum circumferential temperature difference is observed as 55.5 K. The volume fraction of vapor at the absorber outlet are found as 0.31 and 0.37 respectively for DNI 750 W/m2 and 1000 W/m2. The corresponding pressure losses are 316 Pa and 350 Pa, respectively. The obtained results could be employed to characterize the thermal behavior of the DSG solar collectors. The model is useful to configure the solar field operation for optimum performance.